Field of the Invention
Example embodiments relate generally to wireless communication, and more particularly to a method and/or apparatus for use of a small, low-power short-range base station equipped with radio interfaces operating at least two complementary technologies. The two technologies may include a technology based on underutilized or unused spectrum called whitespace spectrum (such as TV whitespace spectrum blocks, RADAR spectrum blocks etc.), and a non-whitespace technology (such as the cellular operator's own licensed spectrum technology, or spectrum bands that are entirely unlicensed and available to all users).
Related Art
Spectrum is a scarce resource in wireless communication systems and is considered especially so in wide-area cellular data communication networks. For instance, in the United States, it is anticipated that cellular data traffic volume will reach several exa-bytes per month by 2014 (1 exa-byte=1 million terabytes), roughly equaling the traffic volume of the entire global Internet demand in 2006, putting a stress on the limited available spectrum.
Besides improving the underlying technologies for wireless communication to relieve the strain on spectrum, two popular approaches to address this challenge include: 1) enabling greater spatial re-use through deployment of many low-power, short-range “mini base stations” (sometimes called “small cells” due to their short-range coverage area), such as indoor femto cells, or outdoor micro, pico cells, and 2) perform cellular traffic offloading to unlicensed spectrum bands (such as WiFi access points). However, the use of “mini base stations” using licensed spectrum bands may cause regular interference with existing full-sized base stations deployed outdoors (often called “macro cells”), and the use of conventional unlicensed spectrum bands (such as 2.4 GHz ISM and 5.8 GHz U-NII bands) do not generally offer a reliable source of capacity.
As demand for new spectrum to increase wireless capacity to meet traffic growth increases, new spectrum bands called “whitespace spectrum” are being considered by the regulatory bodies such as the Federal Communication Commission (FCC). An example of such spectrum bands is the DTV whitespace recently made available by FCC guidelines for opportunistic use in specific scenarios. In the United States, TV whitespace often refers to unused portions of TV broadcast spectrum—specifically lower VHF channels 2-6 (54-88 MHz), upper VHF channels 7-13 (174-216 MHz) and UHF channels 14-51 (470-698 MHz) with the exception of channel 37 which is reserved for radio astronomy. Whitespace is allocated to a primary user (such as a digital DTV broadcaster, a public safety agency, a municipality or government, or an organization or a facility-owner with wireless microphones, for instance). While this whitespace spectrum is generally utilized by the primary user to broadcast TV channels, or broadcast sounds (using wireless microphones), some or all of the spectrum may remain unused or under-utilized for varying periods of time. FCC guidelines now allow a secondary user to use this whitespace on a “do-no-harm” basis, as secondary users may use the whitespace assuming their use does not interfere with the primary user. Therefore, wireless communication service providers may utilize the whitespace spectrum as secondary users. In particular, whitespace may be utilized by wireless communication service providers (secondary users) under three scenarios: 1) a whitespace band may be “unlicensed to secondary users,” meaning that any secondary user may use the band as a secondary user, 2) a whitespace band may be “exclusively licensed to a secondary user,” meaning that only one specifically identified secondary user may use the band as a secondary user, or 3) a whitespace band may be “lightly licensed,” meaning that a restricted number of unidentified secondary users, or a small number of specifically identified secondary users, may use the band as a secondary user. To that end, the FCC has mandated that unlicensed devices be able to either detect the presence of TV stations with a received signal strength as low as −114 dBm and wireless microphones with a received signal strength as low as −126 dBm, or have the capability to contact a TV spectrum occupancy database, so the unlicensed user may know to vacate the band if a primary user is detected in order to guarantee the primary user's use of the spectrum.
Other examples of whitespace spectrum are spectrum bands used by United States Federal Government systems (for example, 3550-3700 MHz used by Naval Radars).